EN CSharp Keyword lock

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C#: lock

Handbook C# · Practical Guide

Executes a mutual exclusion block on the given object or System.Threading.Lock. Does not allow await in a blocked block.

Simple example (Example.cs)

Save this example separately as Example.cs. Run it independently of the other examples on this page.

Example.cs:

// PROJECT-EXAMPLE
var gate = new object();
int count = 0;
lock (gate) { count++; }
System.Console.WriteLine(count);

Result:

1

Syntax

lock (gate) { ... }

Example 1: simple form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

public static class Program
{
    public static async Task Main(string[] args)
    {
        object gate = new(); int counter = 0;
        Parallel.For(0, 20, _ => { lock (gate) { counter++; } });
        Console.WriteLine(counter);
    }
}

Example 2: another practical form

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

public static class Program
{
    public static async Task Main(string[] args)
    {
        System.Threading.Lock gate = new();
        List<int> values = [];
        Parallel.For(0, 10, i => { lock (gate) { values.Add(i); } });
        Console.WriteLine(values.Count);
    }
}

Official source: Microsoft Learn.